<div dir="ltr">Hi Steve the DCD file header is only written once at the beginning of the simulation run. Thus no way to guess how many frames will be dumped during the run eventually. The time for a frame could be retrieved from the print interval and the initial time step which are both dumped, but this works only for a constant time step interval (no variable time step). I am afraid there is no official "DCD standard", but.the CP2K implementation should be quite close to the CHARMM/NAMD definition. It is most important that common tools like VMD are able to digest the DCD files dumped by CP2K even if one could certainly devise a better binary format. Note, that dumpdcd.f90 has also some nice extra feature like <ul><li>definition of first and last frame dumped</li><li>stride (i.e. skipping frames regularily)</li><li>applying PBC (at box centre or at 0,0,0), e.g. useful for movies </li><li>tracing of atoms which leave the original cell</li></ul>Matthias <blockquote class="gmail_quote" style="margin: 0;margin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: 1ex;">OK thanks, that was helpful. So you just read until the end of the file and cp2k doesn't store the number of steps (frames) in the header. And cp2k seems to store the angles directly [a,gamma,b,beta,alpha,c], while lammps stores their cosines [a,cos(gamma),b,cos(beta),cos(alpha),c] and both do this in the same somewhat unusual ordering. Well, this dcd business is really something. Is there an official specification of the format(s)? Anyway, thank you very much for this tool and the fast response. best, Steve -- Steve Schmerler Institut für Theoretische Physik TU Freiberg, Germany </blockquote></div>